Cyclopentadienyl manganese compounds



CYCLOPENTADIENYL MAN COMPOUNDS Tillmon H. Pearson, Baton Rouge, La., assignor to Ethyl Corporation, New :York, N.Y., a corporation of Delaware No Drawing. Application April 25, 1958 Serial No. 730,185

6 Claims. (Cl. 204-59) This invention relates to the manufacture of cyclopentadienyl manganese compounds and more particularly'to the manufacture ofcyclopentadienyl manganese tricarbonyl compounds.

Cyclopentadienyl manganese tricarbonyl compounds have been found to be exceptionally effective antiknocks for use in fuel forpspark plug ignition internal combustion engines. These compounds not only have exceptional effectiveness as antiknocks but also many of these compounds have auxiliary properties which make them practical and desirable forfcommercial use. These auxilia'ry propertiesinclude high solubility in fuels, such as gasoline, and thermo-stability either alone or in gasolines which makes these compounds entirely satisfactory for use under the widely varying conditions to which gasoline and other fuels are normally subjected. Possibly of even greater importance these compounds do not tend to form any appreciable deposits on the engine pistons, valves and spark plug surfaces and likewise are not abrasive to the engine parts as are characteristic of iron compounds. i

It is accordingly an object of this invention to provide an improved process for the manufacture of cyclopentadienyl manganese tricarbonyl compounds. Another object is to provide a process of the above'type using inexpensive raw materials and utilizing a minimum of process steps. Still another object is to provide a process which gives improved yields of the desired. products.

Another object of this invention is to provide a process which has exceedingly fast reaction rates. Other objects and advantages will be more apparent from the following description.

It has now been found that cyclopentadienyl manganese tricarbonyl compounds can be produced in excellent yield by reacting a manganese compound simultaneously with a cyclopentadiene hydrocarbon and gaseous carbon monoxide under the influence of an electric current and in the presence of a transition metal carbonyl. More specifically, the manganese compound is electrolyzed in an electrolyte containing the manganese compound, the cyclopentadiene hydrocarbon and gaseous carbon monoxide, preferably in the presence of an inert diluent,

' especially. one which dissolves the manganese compound or complexes therewith, and particularly a diluent which is also a solvent for the cyclopentadiene hydrocarbon and the carbon monoxide. The transition metal carbonyls useful inthis invention .are particularly those of metals of groups V-'-B, VI-B, VII-B and VIII of periodic table (Handbook of Chemistry and Physics,

- 36th edition, pages 392 and 393).

The cyclopentadiene hydrocarbon and manganese compounds are normally employed in the electrolyte in a molar ratio of from 0.l'to 10 moles of cyclopentadiene compound per mole of the manganese compound. The,

carbon monoxide is, normally used in an excess with respect tostoichiometry and can be employed at pressures of from about atmospheric to about 30,000v p.s.i.g. A more preferred pressure is from about 300 to 5000 manganese tricarbonyl increase many fold.

Patented Dec. 1, 1959 the manganese compound is not dissolved (in excess of.

saturation) since dissolution can take place during the course of the electrolysis as the manganese compound is reacted. Even higher dilutions can be employed but this tends to reduce the current efficiency or reaction rate and also increases the difficulty in product recovery.

The transition metal carbonyl concentration can range from about 0.1.moleto 10 moles per mole of manganese: compound employed in the electrolyte, a preferred con-- cent-ration being from about 0.1 mole to 5 moles of the metal carbonyl per mole of the manganese compound.

The temperature of the electrolysis can vary over a wide range, normally from 0 to 250 C. and preferably from about to 225 C. Lower temperatures can be employed except that the reaction is somewhat slower. Likewise, higher temperatures can be employed except that at the more elevated temperatures some decompositiou is encountered. The preferable temperature somewhat depends upon Whether the cyclopentadiene com pound is employed as a monomer or a dimer in the process. When a dimer is employed, the electrolysis is best conducted at a temperature wherein the dimer will depolymerize to monomer at'an appreciable rate.

Theeffectiveness of the transition metal carbonyl compounds in the process of this invention is very surprising and in fact, the reaction mechanism is not under stood. In the absence of the transition metal carbonyl, the yield of the cyclopentadienyl manganese tricarbonyl compounds is very low, usually ranging below about one percent based upon the electrical current. In contrast, in the presence of even small quantities of the transition metal carbonyl, the yields of the desired cyclopentadienyl This unexpected phenomena is apparently not due to the mere donation of carbonyl groups to the manganese metal by the transition metal carbonyl employed in the process since the reaction does not proceed readily in the absence of gaseous carbon monoxide. In fact, optimum results are obtained in the process with moderate pressures of carbon monoxide.

The compounds which can be made lay-the process of this invention are any cyclopentadienyl manganese tricarbonyl including substituted cyclopentadienyl compounds, such as the indenyl and fluorenyl derivatives. Typical examples of such compounds are cyclopentadienyl manganese tricarbonyl, methylcyclopentadienyl manganese tricarbonyl, n-butyl cyclopentadienyl manganese tricarbonyl, isobutylcyclopentadienyl manganese tricarbonyl, n-decylcyclopentadienyl manganese tricarbonyl, phenylcyclopentadienyl manganese tricarbonyl, methylphenylcyclopentadienyl manganese tricarbonyl, indenyl manganese tricarbonyl and fluorenyl manganese tricar bonyl. For fuel use, the preferred compounds are those containing up to about 12 carbon atoms in the cyclopentadienyl group.

The liquid media which is suitable for the process of this invention can be any solvent or complexing agent for the manganese compound. In general, suitable so vents are ethers, amines, amides, nitriles and the like. The ethers can be either aliphatic or aromatic, such as dimethyl ether, diethyl ether, methylethyl ether, anisole, diphenyl ether and, in general, any ether which is liquid at the reaction temperature and pressure employed. Preferred ethers are the cyclic ethers and the ethylene 3 i glycol type ethcrs. Typical examples are dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, and corresponding higher dialkyl ethers, such as diethyl, methyl ethyl, dibutyl, and the like. Typical examples of diethylene glycol dialkyl ethers are the dimethyl, diethyl, methylethyl, dibutyl and the triethylene glycol ethers including the dimethyl, diethyl, diisopropyl, and the like. In general the preferred ethylene glycol dialkyl ethers have alkyl groups containing from 1 to 6 carbon atoms.

Suitable amine solvents for use in this invention are propyl amine, diethyl amine, di-n-propyl amine, dibutyl amine, triethyl amine, triisopropyl amine, and other amines having from 2 to 10 carbon atoms per alkyl group. Aromatic amines are also suitable, such as aniline, methyl aniline, dimethyl aniline, trimethyl aniline, and similar compounds. A particularly suitable amine solvent is dicyclohexyl amine.

Typical examples of suitable amides are formamide, and the monoand dialkyl formamides, such as N,N'-dimethyl formamide and corresponding compounds with alkyl groups having from 2 to 6 carbon atoms. Other suitable amides are cyclic amides, such as N-methyl pyrrolidone and other alkyl pyrrolidones and amides of inorganic acids, such as hexamethyl phosphoramide.

Suitable nitriles which can be employed as solvents in this invention are acetonitrile, propionitrile, butyronitrile and the like.

With solvents which do not appreciably dissolve or complex with the manganese compound, it is desirable to employ another electrolyte, e.g. a metal salt which does dissolve in the solvent and which will act in the electrolysis to carry the current during electrolysis. Typical examples of suitable electrolytes for this purpose are the alkali, alkaline earth and earth metal halides, such as sodium chloride, bromide, iodide and fluoride, lithium fluoride, potassium fluoride, calcium difluoride, barium dibromide, magnesium dichloride, aluminum trichloride, aluminum tribromide, boron trifluoride and other compounds of these metals, such as the organic salts, e.g. acetate, propionate, and butyrate. Other inorganic salts that can be employed are the sulfides, sulfates, sulfites, nitrates, phosphates, carbonates and the like. Also, very suitable electrolytes for this purpose are complex compounds such as sodium hexacyano maganese (II), sodium aluminum tetraethyl, lithium aluminum tetraethyl, sodium boron tetraethyl and the like.

. Any of the manganous compounds can be employed in this invention, such as the oxide, sulfide, halide, including chloride, bromide, iodide, fluoride, sulfate, carbonate, and nitrate. Of these the halides are preferred and especially the chloride. The organic compounds of manganese are also useful in this invention including manganous formate acetate, propionate, butyrate, oxalate, tartarate, and other salts of organic acids having up to about 10 carbon atoms.

The following examples illustrate the process of this invention. All parts in these examples are given as parts by weight.

ExampleI To an electrolytic cell having manganese electrodes is added in the absence of air or moisture an electrolyte solution containing 32 parts N,N-dimethyl formamide (DMF), 2 parts of manganous chloride, 4 parts of methylcyclopentadiene dimer, 1 /2 parts of iron pentacarbonyl. The cell was pressurized with carbon monoxide to a pressure of 1000 p.s.i.g. A voltage of 25 to 30 volts was applied to the electrodes and the mixture rapidly heated to 195 C. and kept at that temperature for three hours. Under these conditions, the current (average) during the electrolysis was about 0.1 ampere per square centimeter of anode surface. The carbon monoxide pressure in the cell was maintained at 1000 p.s.i.g. throughout the reaction. The electrolyte product, containing the methylcyclopentadienyl manganese triear- 4 bonyl, was thereafter steam distilled to separate the volatile portion of the electrolyte from the non-volatile components, principally inorganic salts. The volatile portion was separated from the water by dccantation and the product purified by fractionation. The yield of methylcyclopentadienyl manganese tricarbonyl was 7 percent, based upon the total current passed through the cell. I

The purified methylcyclopentadienyl manganese tricarbonyl is extremely eifective as an antiknock when used in accordance with the procedures given in US. Patent 2,818,417.

Example II trolysis is conducted at 165 C. using a 500 p.s.i.g. carbon monoxide pressure. The cyclopentadienyl manga-' nese tricarbonyl is recovered in good yield.

Example III The electrolysis of Example I is conducted using a complex manganese salt (Na Mn(CN) and methylcyclopentadiene monomer. The electrolysis is conducted in diethylene glycol dimethyl ether solvent (2 moles per bon monoxide pressure.

mole of manganese compound) in the presence of 1 mole equivalent of Fe (CO) Also, 0.1 moleof sodium chloride is employed to increase the conductivity of the elec-' trolyte. The electrodes in this example are iron. The

electrolysis is conducted at 125 C. and 300 p.s.i.g. car- Similar results are obtained. The product is recovered as in Example I.

Example IV Manganous sulfate is electrolyzed as in Example I except that ethylcyclopentadiene is employed and Fe (CO) is employed as the catalyst. The electrodes in this cell are graphite. The electrolysis is conducted at 225 C., using 8000 p.s.i.g. pressure.

Example V Example I is repeated using manganous acetate and reacting this with indene, the indene being employed in 100 percent excess. The electrolysis is conducted in the presence of cobalt carbonyl, using dicyclohexylamine sol-v vent. One part of lithium bromide is employed .per part of manganous salt to increase the conductivity of the electrolyte. The electrolysis is conducted at 200 C., using 2000 p.s.i.g. pressure. The indenyl manganese tricarbonyl product is recovered in good yield.

Example V I Example I is repeated except that fiuorene is'u sed in place of methylcyclopentadiene and chromium carbonyl (0.8 mole per mole of manganous chloride) is used instead of iron carbonyl. hexamethyl phosphoramide at a temperature of C. and 700 p.s.i.g. carbon monoxide pressure. The fluorenyl manganese tricarbonyl product is obtained in excellent yield.

Example Vll This electrolysis is conducted in 5 Example VIII Example I is repeated except that manganese isopropylate is electrolyzed in the presence of vanadium hexacarbonyl dimer in diethylene glycol dibutyl ether solvent at 180 C., using 950 p.s.i.g. of carbon monoxide pressure. Similar results are obtained.

In the above examples the cyclopentadiene hydrocarbon and metal carbonyl have been reacted directly with the manganese compound. With certain of the metal carbonyls which form complexes with cyclopentadiene, such as the complex dicyclopentadienyl diiron tetracarbonyl, the complex can be used directly in the reaction.

I claim:

1. The process of producing cyclopentadienyl manganese tricarbonyls comprising passing an electrolyzing current from an anode to a cathode through an electrolyte comprising a solution of a manganese compound selected from the group consisting of manganese oxide, manganese sulfide, manganese halide, manganese sulfate,

manganese carbonate, manganese nitrate and manganese salts of organic acids; a cyclopentadiene hydrocarbon; gaseous carbon monoxide and a transition metal carbonyl, said transition metal being selected from the group consisting of metals of groups V-B, VI-B, VII-B and VIII of the periodic table in an inert solvent.

2. The process of claim 1 wherein the solvent is selected from the group consisting of ethers, amines, amides and nitriles.

3. The process of claim 1 wherein the cyclopentadiene hydrocarbon is methylcyclopentadiene.

4. The process of claim 1 wherein the manganese compound is manganous chloride.

5. The process of claim 1 wherein the transition metal is iron.

6. The process of claim 1 wherein the manganese compound is dissolved in dimethylformamide.

No references cited: 

1. THE PROCESS OF PRODUCING CYCLOPENTADIENYL MANGANESE TRICARBONYLS COMPRISING PASSING AN ELECTROLYZING CURRENT FROM AN ANODE TO A CATHODE THROUGH AN ELECTROLYTE COMPRISING A SOLUTION OF A MANGANESE COMPOUND SELECTED FROM THE GROUP CONSISTING OF MANGANESE OXIDE, MANGANESE SULFIDE, MANGANESE HALIDE, MANGANESE SULFATE, MANGANESE CARBONATE, MANGANESE NITRATE AND MANGANESE SALTS OF ORGANIC ACIDS; A CYCLOPENTADIENE HYDROCARBON; GASEOUS CARBON MONOXIDE AND A TRANSITION METAL CARBONYL, SAID TRANSTITION METAL BEING SELECTED FROM THE GROUP CONSISTING OF METALS OF GROUPS V-B, VI-B, VII-B AND VIII OF THE PERIODIC TABLE IN AN INERT SOLVENT. 